Photoacoustic Detection of Superoxide Using Oxoporphyrinogen and Porphyrin

Abstract

The superoxide (O 2 •−) ion is a highly reactive oxygen species involved in many diseases, hence its non-invasive detection is desirable to identify the onset of pathological processes. Here, we employed photoacoustic (PA) spectroscopy, which enables imaging at ultrasound resolution with sensitivity of optical modality, for the first time to detect O 2 •− , using stimuliresponsive contrast agents. Meso (3, 5-di-tert-butyl 4-hydroxyphenyl) porphyrins and oxoporphyrinogens were used as PA contrast agents, which trap the O 2 •− and enable its detection. The trapped O 2 •− increased the PA signal amplitude of chromophores up to 9.6fold, and induced a redshift in the PA signal maxima of up to 225 nm. Therefore, these trigger-responsive probes may be highly valuable as smart diagnostic PA probes to investigate pathological events stimulated by O 2 •− species. Reactive oxygen species (ROS) are highly aggressive, biochemically produced molecules that play important roles in physiological and pathological processes. ROS are a set of short-lived species comprised of O 2 •−

Photoacoustic Imaging Probes Based on Tetrapyrroles and Related Compounds

“…The OxP exhibited completely different optical properties and reactivity than porphyrins. The pristine OxP did not exhibit a NIR-absorption (λ = 654 nm); however, upon capturing the O 2 − , the absorption maximum was redshifted by up to 240 nm and showed an over 10-fold increase in the PA signal (along with the increase in molar absorption coefficient) [86]. Among the variety of ROS and reactive nitrogen species (RNS) explored in vitro, PAI studies showed high selectivity and maximum signal gain for O 2 − (Figure 7c).…”

Recent development of near-infrared photoacoustic probes based on small-molecule organic dye

“…7a ). 96 The complexation of the probes and O 2 ˙ − or F − would cause an enhancement in the PA signal, accompanied by a red-shift in the spectrum. Unlike the probes containing cleavable groups, which exhibit continuous consumption of the substrates, these probes were almost time-independent.…”

Expanded porphyrins: functional photoacoustic imaging agents that operate in the NIR-II region

“…[7][8][9][10] However, most tetrapyrrolic PA systems are limited to the NIR region. 7,11 Absorption greater than 1000 nm, termed the second near-infrared region (NIR-II: 1000-1350 nm), allows for deeper tissue penetration and reduced light scattering than the NIR-I region (700−950 nm). [12][13][14][15][16] Current NIR-II PA contrast agents comprise organic semiconducting conjugated polymers; very few are solely organic-based.…”